The invention concerns a multi-layer body with optical-action elements.
DE 43 34 847 A1 describes a value-bearing document having a window-like opening closed by means of a translucent film. The transparent film provided with a security feature can thus be viewed not only in the incident light mode but also in the transillumination mode. In that respect the security feature can have a thin-layer arrangement and/or diffraction structure having a refraction-optical and/or diffraction-optical effect.
WO 98/15418 discloses a self-verifying security document having a window closed with a transparent plastic material, and a security element. In the region of the window the transparent plastic material has a verification means, for example an optical lens, a polarising structure or an element for producing a moiré effect. To verify the security document the document is folded in such a way that the window is brought into overlapping relationship with the security element and the security element can be viewed through the window. A particular optical effect is afforded by the co-operation of the verification means and the security element.
EP 0 435 029 B2 describes a data carrier, for example a value-bearing paper or bond or an identity card, with a liquid crystal security element, in which a visually invisible coding is disposed under the security element. The security element produces different colour impressions at different viewing angles. Such a liquid crystal is also used in a product by the name of Varifeye®. That product involves a banknote of paper into which a window is introduced, in a similar manner to a watermark. A transparent plastic film into which the liquid crystal and a diffractive OVD (optically variable device) are introduced covers the window. Depending on the brightness of the background the window exhibits different colour effects. Optionally for example black printing can be arranged in the window behind the liquid crystal so that a viewer perceives a colour shift, even if the window is not viewed against a dark background.